Sapondicahon of cellulose esters



Patented Sept. 7, 1937 UNITED STATES PATENT OFFICE England, assignor to Celanese Corporation of America, a. corporation of Delaware No Drawing. Application December rial No. 156,282. In 12, 1933 14 Claims.

This invention relates to the treatment of cellu-' lose acetate and other organic esters of cellulose and particularly to a process for reducing the acidyl content of such esters. The invention is specially applicable to the saponification of filaments, threads, yarns, ribbons and the like made of or containing such esters.

It is well known that caustic soda and other strong mineral bases can be employed to saponify materials that saponification, when effected by such agents, tends to be superficial, so that while the surface of the material is intensively saponified, a core of substantially unsaponified ester remains. Moreover, saponification by such agents when materials may seriously affect the serimetric properties of the materials. It has been discovered that materials comprising organic esters of cellulose can be saponified by means of nonmetallic bases, for example methylamine, ethyl-. ene diamine and other aliphatic amines, particularly those of low molecular weight, in such a way that the s-aponification is relatively deepseated and may even extend throughout the material, while the serimetric properties of the material may actually be improved by the process. I have now found that saponification by means of such non-metallic bases may be considerably accelerated by the presence during saponification of small quantities of caustic sodaor like acting mineral bases without the presence of the caustic soda leading to superficial saponification. The process in fact provides a rapid method of obtaining threads and like materials of good teextensibility and elasticity which are considerable throughout the whole surface or even cross'section.

The mineral alkali is preferably contained in the saponifying bath itself, although other suitable methods of application are not excluded. The quantity of mineral alkali employed should be relatively small. The quantities may be very low, for instance 0.05 to 0.1%, or from 0.2 or 0.5% to 0.8, or above 1%, for instance 1.5 or 2% Preferably the concentration should be relatively low, for instance below 1%. Equivalent concentrations of other strong mineral alkalis may be employed, for instance caustic potash. The material should not be allowed to remain in the bath after saponiflcation is complete.

I The organic of normal or low ester of cellulose treated may be viscosity, for example in the of the type referred to above, but

filaments, threads, ribbons and like depth below the.

6, 1934.8... Great Britain December case of cellulose acetate the viscosity may be of the order of 30 to 50, 100, 200 or even higher, these figures being obtained by comparison of a 6% solution of the ester in acetone at 25 C. with glycerine at the same temperature taken as a standard of 100. Such esters of high viscosity may readily be made by methods in which de radation of the cellulose molecule is substantially avoided during acidylation, for example the methods of U. S. Patent No. 1,708,787. On the other hand, the viscosity of the cellulose acetate employed may be of the order of 10-20 or even lower, or between 20 and 30, me ured on the scale referred to above.

The invention importance in connection with the saponification of filaments, threads, ribbons, ing a basis of cellulose scribed with special reference to such materials.

The materials treated may be made by any suitable dry or wet spinning method. Where high tenacity is required in the final products it is of particular advantage to produce the fila-- ments and the like by wet spinning methods in the course of which they are stretched to a considerable extent, or to soften and stretch the materials after their production whether by a wet or a dry spinning process.- By applying the process of the invention to materials which have been stretched considerably, for example to 200% of their original length or. even more, materials of particularly valuable serimetric properties are obtainable.

Particularly good results are obtained by the use of saponifying baths containing methylamine and caustic soda. Other strong aliphatic organic bases, for example ethylamine, propylamine, amylamine and triethylamine, may also be employed. Again, somewhat weaker bases of the same series, for example trimethylamine and allylamine, may be used. Further, considerably stronger bases of the same series may be employed, even very strong bases such as tetramethyl ammonium hydroxide, provided care be taken to avoid damaging the materials. Again, amines containing more than one amino group, and particularly aliphatic diamines of relatively low molecular weight, for example ethylene diamine, symmetrical dimethylethylene diamine, monoethyl ethylene diamine, and propylene diamine may also be used. Preferably at least one of the amino groups of such amines should be unsubstituted ormonosubstituted. Amines containing more than two amino groups may also be emacetate and will be dethe treatment of 50 tration of 0.010.5%.

ployed, for example 1.2.3-triamino propane. The effect of one or more hydroxy groups in. the amine may, however, be what higher C. or higher, depending on the boiling point of the solution.

into the spinning solutions from which the materials are made. By wayof example, copper oxide may be introduced into the saponifylng When such metals are employed n the saponifying bath it will in general The saponifying medium may swelling agents, solvents or latent solvents for the cue ethyleneether.

When the materials are treated in the form of threads, yarns and the like, it is of adin warp forma- 'centage, for example -30% also contain I into the bath, and after passing through the bath the materials may be drawn by a second roller,

The saponifying agent may be applied by other Thus, for example, the materials in hank extent to which been saponified.

winch dyeing machine.

The materials prior to saponification may be subjected to a treatment adapted to facilitate for example The degree of saponification eifected may be sufficient to reduce the acidyl content of the ester by 8%, 10%

ponification may render the in such mixtures as excellent tensile properties. 5 The following examples illustrate the invenflourenous organic threads and warp formation from a creel through a equivalent of another strong mineral aocaooc Example 1 Cellulose acetate yarn is led continuously in saponiiying bath containing a -20% aqueous solution of mono-methylamine which contains a small quantity, say less than 1% of caustic soda or the alkali. The temperature of the bath is maintained at C. and the rate of travel is adjusted so that the desired degree of sapon'fication is obtained. a

' Example 2 as described in Exbath is The process is carried out ample 1 except that the saponiiying maintained at a temperature of 50"-60 C.

Example 3 l as described in Exsaponifying bath of copper.

Letters The process is carried out ample l or- 2, except that the contains in addition 0.05-0.5%

What 1 claim. and desire to secure by Patent is:--

1. Process for reducing the acidyl content of an organic ester of cellulose comprising saponifying the ester by means of a water-soluble nitrogenous organicbase inwhich eachcarbon atom that is directly attached to a nitrogen atom is directly attached to three other atoms apart from said nitrogen atom in the presence of relatively small quantities of a strong mineral alkali.

2. The process of treating filaments, threads, ribbons and like materials comprising organic esters of cellulose comprising materials by means of a water-soluble nitrogbase in which each carbon atom that is directly attached to a nitrogen atom is directly attached to three other atoms apart from said nitrogen atom in the presence of relatively small quantities of a strong mineral alkali.

3. Process for reducing the acetyl content of cellulose acetate comprising'saponifying the cellulose acetate by means of an aqueous solution of mono-methylamine containing relatively small quantities of a strong mineral alkali.

-.4. Process acetate which comprises passing th continuously in warp formation through an aqueous bath containing from 15-30% methylamine and a quantity of caustic soda less than 1% at -45 C.

5. The process of treating filaments, threads, ribbons and organic esters of ing the materials by means of a lower amine in the presence of relatively small quantities of a strong mineral-alkali. i

6; The process of treating filaments, threads, ri ons and like materials having a basis of org nic esters of cellulose comprising saponifying he materials by means of mono-methylamine i he presence of relatively small quantities of a strong mineral alkali. Ci

'7. The process of saponifying filaments. threads, ribbons and like materials having .a basis of organic esters of cellulose comprising treating the materials with a bath containing a each carbon 'ing the materials water-soluble nitrogenous organic base in which each carbon atom that is directly attached to a nitrogen atom is directly attached to three other atoms apart from said nitrogen atom and small quantities of a strong mineral alkali and of copper in solution.

8. The process of treating filaments, threads, ribbons and like materials having a basis of cellulose acetate comprising saponifying the materials by means of a 15-30% aqueous solution of mono-methylamine containing strong mineral alkali in a concentration equivalent to (Ll-1% of caustic soda.

9. i'he process of treating filaments, threads, ribbons and like materials having a basis of cellulose, acetate comprising saponiiying the materials by means of a 15-30% aqueous solution of mono-mehtylamine containing in solution 0.05-0.5% copper and strong mineral alkali in a concentration equivalent to (ll-1% of caustic soda. 10. The process of threads, ribbons and like materials having a basis of cellulose acetate comprising treating the materials at 50 60 C. with a 15-30% aqueous solution of mono-methylamine containing strong mineral alkali ina concentration equivalent to 0.1-1%-of caustic soda.

11. Process for threads, ribbons and like materials having a basis of organic esters of cellulose, which comprises subjecting the materials to substantially complete saponification by treating the materials with a water-soluble nitrogenous organic base each carbon atom that is directly attached to a nitrogen atom is directly attached to the treatment of filaments,-

saponifying filaments,

three other atoms apart from said nitrogen atom the acetyl content of the materials is reduced by 20-30% by treating the materials with a watersoluble nitrogenous organic base in which each carbon atom that is directly attached to a nitrogen atom is directly attached to three other atoms apart from said nitrogen atom in of relatively small quantities of a strong mineral alkali.

13. The threads, ribbons basis of organic prises treating taining a water-soluble nitrogenous organic base containing pentavalent nitrogen and in which atom that is directly attached to process of saponifying filaments, and like materials having a three other m;-'- and a nitrogen atom is atoms apart from said nitrogen ato strong mineral alkali.

14.-The process of saponiiying filaments, threads, ribbons and like materials having a treat-' 65 basis oli celluloseacetate, which comprises with a medium containing tetramethyl ammonium hydroxide, and a strong mineral alkali. v ROBERT WIGHTON MONCRIEFF,

directly attached to a 

